As a therapeutic method for proliferative organ diseases such as cancer and proliferative lesion in tissues or organs, surgical dissection, irradiation, administration of anticancer agents or combination thereof has been conventionally used. However, basic and specific investigations for the biological characteristics of cancer itself fall behind the remarkable progress of diagnosis technologies for cancer. Therefore, under the present circumstances, drastic therapy of cancer has not been established yet.
Erythropoietin is involved in proliferation and differentiation of hematocytes. Unlike other cytokines, erythropoietin is not produced in hematocyte but produced in kidneys or liver and released into blood. Erythropoietin is considered to act on erythroid burst forming cell (BFU-E) and erythroid colony forming cell (CFU-E) among erythroid precursor cells, stimulate their proliferation and differentiation, and induce production of erythrocytes (Krantz S. B., Blood, Vol. 77, pp. 419–434 (1991)). It has been considered that when erythropoietin binds to a erythropoietin receptor existing on the cell membrane of a precursor cell, a signal is transmitted into the cell nucleus to cause differentiation into an erythrocyte, i.e., accumulation of globin mRNA in the cell, production of hemoglobin and differentiation into an erythrocyte (D' Andrea A. D. et al., Cell, Vol. 57, pp. 277–285 (1989)). However, the detailed mechanism thereof has not yet been clarified, and many problems still remain to be solved.
As the sites on which erythropoietin expresses its gene among tissues except the sites relating to erythroblast, embryos of the early post-implantation stage (Yasuda Y. et al., Develop. Growth Differ., Vol. 35, pp. 711–722 (1993)), brains of humans, monkeys and mice (Marti H. H. et al., Eur. J. Neu. Sci., Vol. 8, pp. 666–676 (1996)) and endometria of mice (Yasuda Y. et al., J. Biol. Chem., Vol. 273, pp. 25381–25387 (1998)) are known. Furthermore, the present inventors have been found that the erythropoietin receptor gene is expressed on mouse deciduae (Yasuda Y. et al., Develop. Growth Differ., Vol. 35, pp. 711–722 (1993)) and vascular endothelium cells of mouse endometrium (Yasuda Y. et al., J. Biol. Chem., Vol. 273, pp. 25381–25387 (1998)) in addition to erythroblasts. Under the present circumstance, the functions of erythropoietin or erythropoietin receptor genes on such sites other than hematocytes have not been revealed yet.
When an embryo nidates on an endometrium, the implantation site of the endometrium undergoes decidual reaction, whereby the deciduae surround the embryo. The erythropoietin receptor gene is expressed on deciduae, whereas erythropoietin is not expressed thereon. Accordingly, it is considered that the erythropoietin receptor is produced on deciduae and bound to the erythropoietin in blood to transmit the erythropoietin signal. According to the investigation on normal human endometrium, expression of the erythropoietin gene could be observed in some samples and could not be observed in other samples by the present technology. However, expressions of erythropoietin and an erythropoietin receptor at the level of protein were observed in all samples. Accordingly, it is considered that erythropoietin is taken from blood or self-secreted at the extremely low concentration in the human normal endometrium, which is similar to the case of the deciduae, and involved in normal physiological function of uterus. On the other hand, it has been recognized by RT-PCR and Southern Blot method that the erythropoietin mRNA is expressed on cervical cancer, corpus uteri cancer, hysteromyoma, ovarian cancer, and ovarian cystoma. Furthermore, an erythropoietin receptor is expressed on the vascular endothelium cells in these cancer tissues. The investigation on these tissues has revealed that erythropoietin and erythropoietin receptor proteins, as well as proliferative nuclear antigens exist on these cancer cells. Accordingly, it was presumed that erythropoietin is involved in proliferation of cancer cells.
Furthermore, it is disclosed that a substance that binds to an erythropoietin receptor in a specific domain can be used for therapy of chronic rheumatoid arthritis (WO00/66632).
Along the way, the present inventors have found that erythropoietin antagonists (the “erythropoietin antagonist” means a substance capable of binding to erythropoietin) such as erythropoietin antibodies, erythropoietin receptor proteins, etc., have an inhibitory effect on proliferation of cancer cells and an interrupting effect on intervening blood capillaries (JP-A-10-101574, British Journal of Cancer, Vol. 84, pp. 836–843 (2001)).